Samsung Galaxy S8 vs. Samsung Galaxy S9 battery life

If you’re on the fence about upgrading to the Samsung Galaxy S9 or S9 Plus from your S8 or S8 Plus, you’ll want to know what the difference in battery life will be like. Now that we’re taking deeper dives on the products we review, we can shed some light on the situation. After testing all four phones several times, we found that you should probably keep the S8 if battery life is your main concern.

You should probably keep the S8 if battery life is your main concern.

In our labs, we tested all four phones using our default battery testing protocols. In both HD and WQHD+ modes, the Samsung Galaxy S8 and S8 Plus beat their counterparts in battery life — while matching them in recharge time. To prepare the phones for our tests, we set each unit’s screen to 200cd/m2, ensured it was fully charged and that the phones weren’t running any non-system processes in the background.

Both the Samsung Galaxy S8 and the S8 Plus last longer than their S9 counterparts.

But here’s the rub: you could also just switch your new S9 or S9 Plus to the HD mode to save battery life when it’s not absolutely necessary to have your phone displaying WQHD+ content. If you haven’t messed with the settings on your phone until this point, Samsung has all four of these phones set to HD mode by default. While each of these tests were run several times to reduce sample variation, we did notice that the S9 Plus struggled with mixed use in WQHD+, the reason for which we can’t pin down.

Video playback

Easily the most forgiving of the three tests we ran, the Samsung Galaxy S8 and S8 Plus last longer than 700 minutes in both HD and WQHD+ modes. While the S9 and S9 Plus don’t lag too far behind, the upgraded system obviously needs a little more juice to run. At worst, the S9 lags 80 minutes behind its S8 counterpart. That may sound like a dealbreaker, but it only really amounts to an 11 percent shortfall. I’ve kept the axis minimum on all the following charts at zero to illustrate what I mean.

The Samsung Galaxy S9 and S9 Plus lag behind in video performance, but not by a high percentage.

The only outlier result here is the Samsung Galaxy S9’s WQHD+ performance, which is a little strange, but not unexpected. This would probably be most pronounced if you were to use the phone for VR, but otherwise the HD mode should suffice for day-to-day use. A result of 621 minutes is still over 10 hours of constant playback, so it’s tough to throw shade here.

Web browsing

Here too, the 3,000mAh battery of the S9 falls a little short. Considering it’s using a much more powerful processor, that’s not very surprising. Again, we see battery life drop less than 10 percent. Web browsing can still go for about eight hours straight, it’s still tough to knock.

Again, the Samsung Galaxy S8 and S8 Plus reign supreme.

Obviously, this will vary if you’re using the screen at a higher brightness than 200cd/m2, but the automatic brightness tends to land somewhere near that setting (roughly 64-66 percent for all models listed) indoors. If you max the brightness, you can expect your battery life to tank a bit.

Mixed use

Our mixed-use app test cycles through different use cases at set intervals to see how well a phone could handle someone who bounces around between web browsing, watching video, and gaming. As this is a fairly punishing test, the battery savings between using the HD vs. the WQHD+ display mode is far more apparent.

The effect of the 4K display mode on battery life is significant.

The change in battery life between 4K and HD tests doesn’t always follow what you’d expect from the battery size. The Samsung Galaxy S8 and S9 Plus saw a drop-off of almost 25 percent.

Conclusion

Processor aside, the Samsung Galaxy S8 and S8 Plus are remarkably similar phones— they both even have better in battery life than their newer counterparts. If you’ve been waiting to upgrade until you could verify how good the new phones are for battery life, I’d say you may want to sit the S9 out and hold on for another year. The changes to the phone were already minimal, and with the older handset posting better battery life scores, how necessary is that ultra-overkill processor?

Those hunting for a bargain and a credible daily driver may decide the S8 or S8 Plus is a better buy than the S9 and S9 Plus.